Explain Belady's Anomaly?

Also called FIFO anomaly. Usually, on increasing the number of frames allocated to a process' virtual memory, the process execution is faster, because fewer page faults occur. Sometimes, the reverse happens, i.e., the execution time increases even when more frames are allocated to the process. This is Belady's Anomaly. This is true for certain page reference patterns.

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Explain Belady''s Anomaly?
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It is a useful, memory-saving technique for multiprogrammed timesharing systems. A Reentrant Procedure is one in which multiple users can share a single copy of a program during the same period. Reentrancy has 2 key aspects: The program code cannot modify itself, and the local data for each user process must be stored separately. Thus, the permanent part is the code, and the temporary part is the pointer back to the calling program and local variables used by that program. Each execution instance is called activation. It executes the code in the permanent part, but has its own copy of local variables/parameters. The temporary part associated with each activation is the activation record. Generally, the activation record is kept on the stack.

Note: A reentrant procedure can be interrupted and called by an interrupting program, and still execute correctly on returning to the procedure. (More...)

Manifest is metadata about assemblies. Metadata is machine-readable information about a resource, or ""data about data." In .NET, metadata includes type definitions, version information, external assembly references, and other standardized information. (More...)

Life cycle of ASP.Net Web Form Page Request >> Start >> Page Init >> Page Load >> Validation >> PostBack Event Handling >> Page Rendering >> Page Unload Page Request - When the page is requested ASP.Net determines whether the page is to be parsed and compiled or a cached verion of the page is to be sent without running the page. Start - Page propertied REQUEST and RESPONSE are SET, if the page is pastback request then the IsPostBack property is SET and in addition to this UICulture property is also SET. Page Initilization - In this the UniqueID of each property is SET. If the request was postback the data is not yet loaded from the viewstate. Page Load - If it was a postback request then the data gets loaded in the control from the ViewState and control property are set. Validation - If any control validation present, they are performed and IsValid property is SET for each control. PostBack Event Handling - If it was a postback request then any event handlers are called. Page Rendering - Before this the viewstate is saved from the page and RENDER method of each page is called. Page Unload - Page is fully rendered and sent to the client(Browser) and is discarded. Page property RESPONSE and REQUEST are unloaded. (More...)

Manifest is metadata about assemblies. Metadata is machine-readable information about a resource, or ""data about data." In .NET, metadata includes type definitions, version information, external assembly references, and other standardized information.

Metadata: Metadata describes contents in an assembly classes, interfaces, enums, structs, etc., and their containing namespaces, the name of each type, its visibility/scope, its base class, the nterfaces it implemented, its methods and their scope, and each method's parameters, type's properties, and so on.

Readystate property holds the response of the server to the query generated from the client side. Each time the readystate property changes onreadystatechange function will be executed. Some of the values for the readystate property are as follows if the status is zero the request is not initialized, 1 the request has been set up, 2 the request has been sent, 3 the request is in process, 4 the request is complete. (More...)

Notification Services applications are based on a subscriber/subscription model. The Key components in a Notification Services application are

Subscriber: A user or application that requests and receives the notification Subscription: A request for information, delivery mechanism, and destination for requested notifications. For example change of a stock price. Event: A piece of information, in which the subscriber is interested. For example as soon as a stock price has changed an event can be generated that's processed within SQLNS.Notification: A message containing the information requested by the subscriber in the subscription.

SQLNS executes the following steps whenever it generates a new notification and sends it to registered subscribers:

.Subscribers create subscriptions with a subscription management application, such as an ASP.NET or Windows Forms front end..Subscription management is the only part of an SQLNS application where users or applications are actively involved in the process. You generate subscriptions using a managed assembly shipped with SQLNS. .The Notification Application collects events, which are processed within the SQLNS application. .SQLNS uses T-SQL statements to assign events to the subscriptions registered in the first step. .SQLNS generates new notifications whenever it finds an assignment. .A Formatter formats the new notification, and SQLNS delivers it through a delivery channel to the registered target device of the subscriber. (More...)

Snapshot replication: Snapshot replication distributes data exactly as it appears at a specific moment in time and does not monitor for updates to the data. Snapshot replication is best used as a method for replicating data that changes infrequently or where the most up-to-date values (low latency) are not a requirement. When synchronization occurs, the entire snapshot is generated and sent to Subscribers.

Transactional replication:

Transactional replication, an initial snapshot of data is applied at Subscribers, and then when data modifications are made at the Publisher, the individual transactions are captured and propagated toSubscribers.

Merge replication: Merge replication is the process of distributing data from Publisher to Subscribers, allowing the Publisher and Subscribers to make updates while connected or disconnected, and then merging the updates between sites when they are connected. (More...)

Data integrity is an important feature in SQL Server. When used properly, it ensures that data is accurate, correct, and valid. It also acts as a trap for otherwise undetectable bugs within applications.

A PRIMARY KEY:

A PRIMARY KEY constraint is a unique identifier for a row within a database table. Every table shouldhave a primary key constraint to uniquely identify each row and only one primary key constraint can be created for each table. The primary key constraints are used to enforce entity integrity.

UNIQUE constraint:

A UNIQUE constraint enforces the uniqueness of the values in a set of columns, so no duplicate values are entered. The unique key constraints are used to enforce entity integrity as the primary keyconstraints.

FOREIGN KEY constraint:

A FOREIGN KEY constraint prevents any actions that would destroy links between tables with the corresponding data values. A foreign key in one table points to a primary key in another table. Foreignkeys prevent actions that would leave rows with foreign key values when there are no primary keys with that value. The foreign key constraints are used to enforce referential integrity.

CHECK constraint:

A CHECK constraint is used to limit the values that can be placed in a column. The check constraints are used to enforce domain integrity. A NOT NULL constraint enforces that the column will not accept null values. The not null constraints are used to enforce domain integrity, as the check constraints. (More...)

these cursors are invoked implicitly. User need not create, open, fetch or close the cursor.

Explicit cursors:

these cursors are not invoked implicitly. User needs to create, open, fetch or close the cursor.

Static Cursor:

Stores a complete copy of the result set. Used mostly where scrolling is required. Static cursors don't support updates.

Forward -only cursors:

This cursor supports updates but not scrolling. It supports only fetching serially. Rows are not retrieved from the database until they are fetched.

Forward - only cursors /Read only cursor:

These are the fastest of the cursors and cannot be updated. They cannot be created on query that returns only read only columns.

Key set driven:

It is a scrollable cursor that cannot be updated. These cursors are controlled by a set of physical identifiers called as key set. The keyset is built in a temporary table when the cursor is opened. (More...)

ADO.NET has two primary parts in its architecture out of which one is data provider. It has its own set of objects and it consists of its own classes. Some of them are connection, parameter, data reader, command and data adapter. This provides access to data sources such as Oracle, SQL server, etc. (More...)

This base class is added to ADO.NET 2.0. This class facilitates the process of obtaining a list of data sources. SQL server returns instances that are available on the network. Programmers do have choice of tools in their hands with this feature. (More...)

Language integrated query or LINQ provides developers to query data. It uses strongly typed queries and results. Developer productivity increases by the usage of compile time error checking and intellisense. This feature is common on number of data types. (More...)

Language integrated query or LINQ provides developers to query data. It uses strongly typed queries and results. Developer productivity increases by the usage of compile time error checking and intellisense. This feature is common on number of data types. (More...)

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